The overall aims are tow-fold: first, to characterize the magnitude of intra- and intermolecular motion and conformational changes of the contractile proteins actin and myosin during ATPase activity; secondly to identify in molecular terms how energy transduction occurs in skeletal muscle through further detailed study of the myosin, actomyosin and myofibrillar ATPase mechanisms. The magnitude of protein conformation changes in muscle proteins will be studied by measurement of distance changes as detected through the use of spectroscopic probes. Dynamic processes of the myosin and actomyosin ATPase are well characterized and the structural changes associated with these processes will be measured using energy transfer as detected by fluorescence changes. The myosin and actomyosin ATPase mechanisms will be studied by transient kinetic, NMR and 18O-isotopic methods. These methods are particularly appropriate to help find out how the organized protein lattice of the sarcomere influences the ATPase mechanism. Medically the relevance of this program is that it will provide at the molecular level better understanding of how skeletal and less directly cardiac and smooth muscle function.